1. Field of the Invention The present invention relates to a method of tamping a track with a track tamper running along the track on two undercarriages in an operating direction, which comprises the steps of generating an optical reference line determined by two reference points, each reference point being formed by a sensing element running along the track on a flanged roller, a first one of the sensing elements being positioned ahead of the track tamper in the operating direction and a second one of the sensing elements being positioned between the undercarriages, and measuring the position of the track in relation to the optical reference line. It also relates to a track tamper useful for carrying out this method.
2. Description of the Prior Art
U.S. Pat. No. 3,545,384 discloses a track tamper comprising a machine frame running on two undercarriages along the track in an operating direction. A tamping unit for tamping the track and a track position correcting unit are mounted on the machine frame. To correct the track position, a track position measuring system with a light beam reference line is used. The reference line is defined by a first reference point preceding the track tamper in the operating direction and a second reference point positioned at the track position correcting unit. The reference line is brought into a position extending parallel to the desired track position. A receiver having two light-sensitive cells forms the second reference point, the light-sensitive cells being spaced from each other in a vertical direction by a predetermined distance. Thus, the reference beam causes two different pulses which are used to control the tamping unit and the track position correcting unit.
It is known from Austrian patent No. 314,580 to control track lining tools by a laser beam emitter. In this machine, a laser beam is directed onto a fixed reference point laterally adjacent the track. This enables the track to be lined by moving it laterally until the reference beam registers with a mark on the fixed reference point.
According to European patent No. 401,260, a reference line ahead of a measuring bogie is defined by a reference point determined by known coordinates and a reference point positioned in the center of a receiver formed by a multiplicity of photo cells. In connection with a distance measuring instrument, the deviation of the second reference point from a desired position can be determined.
Finally, Austrian patent No. 328,490 discloses yet another type of track position correcting machine with a reference system preceding and comprising a reference line determined by two reference points.